Pension Exemption Help

I'm a exchange student (F20) living in Kanagawa and just had my 20th birthday on October, and will live in Japan until early February.

Around one month ago, I received the letter from Japan's Pension Service regarding how I should pay my pension. After I informed my university, they helped me to write an exemption form and send it to the government.
I thought that's it, but I'm wrong.

Around two weeks ago, arrived a letter that when I translated, it said that they don't accept my pension exemption. I consulted with my university, but they just said I can ignore it and throw it in the trash because the exemption procedure is probably still happening, so I did so.

To my surprise, today came a bill from the pension service. It's really expensive, and I can't pay for it (I just lost 100.000 yen recently, that's a whole another story). I consulted my campus, and surprise, they said to just ignore it. However, I am really concerned, because it seems like ignoring this is a crime. What should I do? Should I go to nearest city center? Any advice is truly appreciated.

by butterflynaka